Oscillation generator



Dec. 12, 1939. KWMRWS HAL 2,182,870

' OSCILLATION GENERATOR Filed Dec. 24, 1956 2 Sheets-Sheet 1 5/4 3 OUIPl/T INVENTORS KENN ETH w. JARVISAND RUSSELL M. BLAIR BY w flw w ATTORNEY 1939- K. W/JARVIS ET AL 2,182,870

OSCILLATION GENERATOR Filed Dec. 24, 1936 2 Sheets-Sheet 2 43 Iflfilk l l l l" INVENTORS KENNETH W. JARVIS AND BY RUSSELL'M. BLAIR m ATTORN 0.. a ing in some respects to the well known three element grid controlled oscillator, but having Patented Dec. 12, 1939 UNITED STATES PATENT OFFIQE OSCILLATION GENERATOR poration of Delaware Application December 24, 1936, Serial No. 117,659

3 Claims.

The present invention relates to oscillation generators and in particular, circuit arrangements adapted for use in connection with the operation of electron and vacuum tubes of the general type described in the U. S. Patent No. 1,903,569 issued April 11, 1933, to us and for which a reissue application Serial No. 16,108 has been filed on April 8, 1935. This reissue is No. 20,545, granted November 2, 1937. Still further, this invention relates to the use of primary and secondary electron streams and associated tube and circuit elements and operating potentials for producing systems capable of oscillation.

In the prior art of generating oscillation utilizing electronic discharges, difiiculties were encountered due to limitations of operating characteristics with respect to frequency, stability, efficiency, and control. Our present invention substantially overcomes these limitations by providing primary and secondary streams of electrons and ways and means for preventing the secondary stream from spuriously reacting upon the primary stream.

It is an object of this invention to provide a means for converting direct potentials into alternating potentials of any frequency, being limited only by transit time of the electrons.

A still further object of this invention is to provide a new type of oscillator.

Another object of this invention is to provide an oscillation system where no undesirable or uncontrollable coupling elements are introduced.

A further object of this invention is to produce a dynatron oscillator wherein higher efliciencie's may be obtained.

Another object of our invention is to provide an electronic oscillator. with relatively low plate power loss.

A still further object of our invention is to provide an electronic, oscillator whose frequency characteristic is substantiallyindependent of the oscillators output.

An object of our invention is to provide an electronic oscillator whose frequency determining circuit is substantially isolated from its output circuit.

Other and further objects are disclosed in the following description and in the attached claims.

In the attached drawings,

Fig. 1 is a simple oscillator circuit correspondsome advantages over this known type;

Fig. 2 portrays the current in the collector plate of the tube structure referred to previously,

with respect to the collector plate potential showing a negative resistance characteristic,

Fig. 3 shows an oscillation circuit making use of the negative resistance characteristic;

Fig. 4 shows the circuit of a new type of oscil- 5 lator, and

Fig. 5 shows the current relationship in an oscillator as shown in Fig. 4.

In Fig. 1, the tube I comprises the emitter 2,

the control grid 3, the collector plate 4, the .0

output plate 5, and the shielding element 6. The sources of potential, 1, 8, 9, l and II, serve to render the emitter thermionically emissive, and the other elements in the order named, properly operative. prises the inductance I2 and the condenser 13, while the inductance M acts as a tickler to feed back energy to the oscillation circuit. The grid leak l and by-pass condenser l6 are used in the control electrode-cathode circuit as in conventional oscillators. As the principle of operation ,of such oscillators is well known, no additional description is added. However, in the usual oscillator, there is a capacity coupling between the output plate and the control grid.

This often causes undesirable efiects such as an uncontrollable feedback, parasitic oscillations, and other deleterious features well known in the art. In the circuit and tube arrangement shown,

the only feedback is through the controllable element It and all the above disadvantages are avoided.

The potential of the source In is made sufficiently high to draw to the output plate 5 all the secondary charges emitted by the collector lators known to the art have a quite high power loss in the plate resistance which greatly reduces their efiiciency of conversion of d. c. to a. 0., compared to the arrangement of this invention.

Fig. 2 shows the variation in current flowing in the lead ll of Fig. 3, with respect to the potential 18 applied thereto. The current starts from zero, increases in a positive direction as the potential is raised. As the potential is raised, the velocity of the striking electrons increases,

and drives ofi secondary charges from the elecv The oscillation circuit com- 16 trode 25. These charges flow to an output plate 26 as previously described. At the point [9, the flow of secondary charges has increased to an amount to prevent further increase in In. A still further increase in E18 produces more secondary charges and In falls. At the point 20 in Fig. 2, the secondary charges leaving the collector plate equal the primary charges arriving, and give no current I17. Further in the same positive direction with E18 gives more secondary charges, and the current I17 reverses as shown by the negative value. About the point 2| a new effect comes into play as the potential E17 approaches the output plate potential E22 of Fig. 3. The output plate potential no longer is relatively positive sufficient to draw over all the secondary charges, so the loss to I17 decreases, and In increases as shown. If E18 be made greater than E22, I17 will reach in value the total primary emission as a limit. The region of 111 between the points [9 and 2! shows a decreasing current with an increasing voltage, which is in effect a negative resistance characteristic. If a tuned circuit having a positive resistance equal to the negative resistance (an average condition equalized by non-linear factors during oscillation) be connected in the negative resistance circuit, oscillation will result as is well known.

The complete circuit is shown as Fig, 3, where the tube structure is shown at 23. The emitter 24, the collector plate 25, the output plate 26 and the shielding element 21 are indicated. The source of potential 28 heats and renders thermionically emissive the emitter 24, and the sources of potentials I8, 22 and 29 serve to render the other elements operative in the order named. The potential [8 is preferably adjusted to a fixed value about the mid position of the values corresponding to points l9 and 21 of Fig. 2. The tuned circuit serving as the oscillator circuit includes the inductive impedance 3!] and the tuning condenser 3|. When the potentials are properly adjusted, the circuit oscillates as described and oscillating energy may be had from the secondary of 3!]. It will be appreciated that the element 38 may be a simple inductance and oscillating energy derived from the circuit electrostatically or by other electromagnetic means of coupling.

In the customary dynatron oscillators, the output element is in the form of a grid through which the primary charges flow, striking a secondary emitter further along in the direction of travel. Secondary charges travel in opposite direction, back to the higher positive potential grid, A similar negative resistance effect is produced at the secondary emitter in this system. However, in the devices known to the prior art, the output grid element interposed in the path of the primary stream absorbs much of the initial primary stream before it has a chance of producing secondary emission. This lowers the negative resistance effect (the negative resistance has a higher numerical value) and so the ability of the device to act as a power generator is likewise lowered. In the invention as shown, this defect is avoided, as all primary emission reaches the collector plate 25 and only the secondary emission reaches the output plate 26. This results in the high ratio of secondary to primary emission being completely usable. This makes for a very low negative resistance and an admirable oscillator under conditions which would spell failure for conventional dynatron devices.

Fig. 4 shows a novel and useful circuit arrangement which is a feature of our invention. The secondary emission tube structure 32 comprises elements as follows: emitter 33, control grid 34, collector plate 35, output plate 36 and shielding element 31. These elements are properly and respectively made operative by the sources of potentials indicated at 38, 39, 40, 4i and 42. In the input circuit of the control grid 34, is inserted the inductance 43 connected in parallel with the tuning condenser 44 forming an oscillatory circuit. In the collector plate 35 circuit is connected the inductance 45, inductively coupled to the inductance 43, serving as a tickler. In the output plate 35 circuit is connected the tuned circuit comprising the inductance 50 in shunt to the condenser The internal tube currents are indicated at 4B and 49.

Referring now to Fig. 5, the action of the oscillator shown in Fig. 4 will be explained. Fig. 5 shows, neglecting certain slight phase shifts often present in an oscillator, the relationships between control grid 34 potential and several tube currents. Instantaneous values are shown against time, It will be observed that as the control grid potential gets more positive, the primary emission stream 148 also increases. This is exactly the same as in any normal triode. In the normal triode oscillator, this current 148 would flow out from the plate and through the tickler 45 and make the tube oscillate. In this case, however, the primary emission reaching the collector plate 35 dislodges a greater number of secondary charges which as I49 flow to the output plate 36. The current flowing out of the collector plate 35 is the difference between I43 and I49, and due to the secondary emission ratio, I49 is the greatest and I47 is negative as shown. It follows the same phase as the primary emission I48 but is reversed in sign. As a result, in order to make the equiva lent (emitter-control grid-collector plate) triode oscillate, the sign of the tickler mutual inductance must be reversed from that customarily necessary. This reversal is indicated in the crossed leads 46 and 41 in Fig. 4.

This novelty is not the only point of distinction of the circuit of Fig. 4. When this initial equivalent triode section is oscillating, a varying current will flow as I49, If the tuned circuit 50-5l be tuned to this frequency of oscillation, it will absorb this a. 0. power and may in turn supply it to other circuits as desired. If the potential 4| be maintained high enough so that the negative values of voltage across the tuned circuit 5fl5l do not drop the sum of its voltage and the source 4| below the saturation potential, the impedance looking back into the output plate 35 will be infinite, using saturation in the same sense as the art does. This means that variations in the output circuit conditions cannot affect the tube conditions and so not change the oscillation frequency. This is a very important improvement, for in other tube oscillation circuits the load circuit and the frequency-determining circuit are oneand the same. As a result, in the prior types of oscillators any change in load con-' ditions affects the oscillation frequency, an effect generally most deleterious. In the circuit of this invention shown in Fig. 4, these two necessary frequency-determining and load circuits are completely independent, with the resulting attendant advantages of high frequency stability.

Having described our invention, what We claim I 1. An electronic oscillator comprising asource of primary electrons, a secondary emissive elecposed between said source and said emissive electrode, a feed-back inductance connected in series with a source of potential between said source of primary electrons and said electrode for controlling the number of primary electrons reaching said electrode, a control electrode interposed between said source and said emissive electrode, means connected between said control electrode and said cathode for receiving energy from said inductance, a secondary electron collecting electrode, an output circuit connected between said collecting electrode and said cathode and an electrostatic shield interposed between said source of primary electrons and said collecting electrode.

2. An electronic oscillator comprising a source of primary electrons, a secondary emissive electrode, a feed-back inductance connected in series with a source of potential between said source of primary electrons and said electrode for controlling the number of primary electrons reaching said electrode, a secondary electron collecting electrode, an electrostatic shield interposed between said source of primary electrons and said collecting electrode, a. control electrode intertrode, and a tuned circuit "connected between the control electrode and source, said tuned circuit being coupled to the feed-back inductance.

3. An electronic oscillator comprising a source of primary electrons, a secondary emissive electrode, a feed-back inductance connected in series with a source of potential between said source of primary electrons and said electrode for con trolling the number of primary electrons reaching said electrode, a secondary electron collecting electrode, an electrostatic shield interposed between said source of primary electrons and said collecting electrode, a control electrode interposed between said source and said emissive electrode, a tuned circuit connected between the control electrode and source, said tuned circuit being coupled to the feed-back nductance, a tuned circuit connected between the collecting electrode and. said source, and an output circuit coupled to said tuned circuit.

KENNETH W. JARVIS. RUSSELL M. BLAIR. 

